Nuclear rockets for Mars: US tests fuel at 3,992°F for faster human space travel

Experiments on nuclear thermal rocket fuel coatings were performed by the team at the Ohio State University Research Reactor.

“Our experiment aimed to test a fuel coating technique and evaluate if it can withstand the intense environment of a nuclear thermal rocket,” said Brandon Wilson, an R&D staff member in ORNL’s Nuclear and Extreme Environment Measurement group. 

“Testing materials at exceptionally high temperatures is a first and a crucial step toward helping NASA mature and qualify nuclear fuels for manned space exploration using nuclear thermal propulsion technology,” added Wilson.  

Protecting nuclear reactor

NTP engines heat hydrogen with nuclear reactors to generate thrust. This technology could facilitate faster travel to Mars and reduce overall mission costs. 

However, the extreme conditions inside an NTP engine pose a major challenge. This is where ORNL’s expertise in material science comes into play.

ORNL developed a zirconium carbide coating that protects reactor core materials from hydrogen damage without affecting reactor performance.

After the development, the team tested the coating under realistic conditions, simulating the intense heat and radiation of an operating NTP engine. 

The In-Pile Steady-State Extreme Temperature Testbed (INSET) — a purpose-built high-temperature furnace — facilitated the in-reactor testing.

INSET 2.0 is the only technology that rapidly heats materials to 3992 degree Fahrenheit (2200°C) for post-irradiation handling. Moreover, INSET’s adaptable design allows it to be used in any research reactor with a port over eight inches.

Therefore, it is suitable for experiments both inside and outside reactors.

Testing of coating

The experiment involved placing four distinct samples of nuclear thermal rocket fuel surrogates, each coated with zirconium carbide, into the INSET apparatus. 

Over two days, these samples were subjected to repeated cycles of varying temperatures while being irradiated.

This rigorous testing regimen aimed to simulate the harsh conditions expected within a nuclear thermal propulsion engine. It allowed researchers to evaluate the durability and protective capabilities of the zirconium carbide coatings. 

This experiment is a vital step in the process of developing the necessary materials for future space travel.

The next step is post-irradiation analysis at ORNL. The team will perform analysis to assess how well the coatings performed after irradiation as well as operational fuel protection capabilities. 

“The findings from this experiment will represent a crucial step in advancing nuclear thermal propulsion technology for future human space exploration,” said Wilson in the press release. 

Going to Mars is not a straightforward way. Mars launch windows occur roughly every 26 months. Traditional rockets may take 150-300 days to reach Mars.

If successful, NTP-based spacecraft could significantly reduce this travel time.